1. Field of the Invention
The present invention relates to a composite drive system, for a compressor, capable of rotationally driving the compressor selectively or at the same time by either of two drive sources including a prime mover such as an internal combustion engine and a motor rotated by the power of a battery.
2. Description of the Related Art
To cope with the environmental problems in recent years, the practical application of an idle-stop (or “eco-run”) system has been promoted for stopping an internal combustion engine when a vehicle such as an automobile, with the engine mounted thereon, has stopped. When this system is used, as long as the vehicle is stationary, the compressor of the air-conditioning system of the particular vehicle also stops and the air-conditioning system is turned off, thereby causing the vehicle occupants to feel uncomfortable. In view of this, a “hybrid compressor” is known which can be driven by either of two drive sources. Specifically, while the vehicle is stationary, the drive source is switched from the internal combustion engine to a motor rotationally driven by the power stored in a battery thereby to drive a compressor.
As a first well-known example of the hybrid compressor, a system capable of driving a swash-plate compressor selectively by one of two drive sources, including an internal combustion engine and a battery, has been proposed. In this system, a pulley having an electromagnetic clutch widely used for an automotive air-conditioning system is mounted on the drive shaft of a swash-plate compressor with the discharge amount thereof variable for each rotation. This pulley is adapted to be rotationally driven by the internal combustion engine through a belt. On the other hand, a motor driven by battery power is mounted on the drive shaft of the same compressor. In the normal operating mode of this system, the compressor is driven by the internal combustion engine, and when it is foreseen that the time has come to stop the engine or switch the drive source of the compressor from the engine to the motor, the angle of inclination of the swash plate of the compressor, changing with the magnitude of the cooling load, is detected. In the case where the inclination angle is large, indicating that the cooling load is heavy, the deenergization of the electromagnetic clutch and the stopping of the internal combustion engine are delayed. Thus, the compressor continues to be driven by the internal combustion engine. In the case where the cooling load is light and, therefore, the inclination angle of the swash plate is small, on the other hand, the electromagnetic clutch is immediately deenergized while at the same time stopping the internal combustion engine. Thus, the compressor is driven by the motor.
In a second well-known example of the hybrid compressor described in Japanese Unexamined Utility Model Publication No. 6-87678, as in the first well-known example, the drive shaft of the swash-plate compressor is rotationally driven selectively by two drive sources, i.e. by an internal combustion engine connected to the drive shaft of the swash-plate compressor through a belt, a pulley and an electromagnetic clutch, or by a motor driven by the battery directly and connected with the drive shaft of the compressor. The feature of this conventional hybrid compressor lies in that, while the compressor is driven by the internal combustion engine, the same motor is used as a generator from which power is acquired and stored in a battery.
The first well-known example of the hybrid compressor poses the problems that a swash-plate compressor of a variable displacement type having a complicated structure is used to make the discharge capacity variable, that the motor is only an auxiliary drive source for driving the compressor temporarily while the internal combustion engine is out of operation and is useless in other points, that a complicated control operation is required in spite of the rather poor functions and effects, and that the pulley for receiving the power from the internal combustion engine is very bulky because the electromagnetic clutch and the motor are built inside of the pulley.
On the other hand, the problems of the second well-known example of the hybrid compressor are that a swash-plate compressor of a variable displacement type having a complicated structure is used to make the discharge capacity variable, and that an electromagnetic clutch and a motor are built inside the pulley in radially superposed positions and therefore the pulley is bulkier than that of the first well-known example of the hybrid compressor. In the second well-known example, however, the motor is used also as a generator. Therefore, although this motor is not a simple auxiliary drive source used selectively in coordination with the internal combustion engine, the additional function of the motor for power generation is undesirably overlapped with the operation of the generator for charging the battery always attached to the internal combustion engine. Also, the motor for power generation is not used in other than the season when the cooling system is operated, and therefore the generator attached to the internal combustion engine cannot be eliminated and replaced by the motor. Thus, the use of the motor for driving the compressor as a generator leads to no special advantage. Both of the conventional hybrid compressors described above, therefore, have no greater advantage than the basic functions and effects of selectively using two drive sources at the sacrifice of a complicated compressor structure and the resulting considerably increased volume of the compressor and the related component parts.